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Uni-LoRA: One Vector is All You Need
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Proposes Uni-LoRA, a unified projection view of LoRA variants, and a frozen, isometric random one-hot-column-normalized projection that lets a single trainable vector of length d reconstruct all LoRA parameters.
Problem
Existing LoRA parameter-reduction variants (Tied-LoRA, VeRA, LoRA-XS, VB-LoRA) use layer-local or non-isometric projections, limiting parameter efficiency and sharing across layers; a unified view and a more efficient, geometry-preserving reduction are needed.
Approach
View LoRA parameters as a D-dimensional vector and all LoRA variants as a fixed or learned projection P from a d-dimensional subspace; propose a globally random uniform projection (each row one-hot at a random slot, column-normalized by 1/sqrt(n_j)) that is provably isometric, is O(D) to apply, and needs only one trainable vector.
Key results
- On GLUE with RoBERTa-large, Uni-LoRA reaches 88.3 average with 0.023M trainable parameters, versus 87.8 for LoRA (0.786M) and 88.2 for VB-LoRA (0.162M).
- On GSM8K/MATH with Gemma-7B, Uni-LoRA (0.52M params) scores 75.59 on GSM8K and 28.94 on MATH, above LoRA's 74.90 and 31.28 only on GSM8K; it trails LoRA on MATH.
- On ViT-Base vision tasks, Uni-LoRA (72K params) averages 85.15 versus 77.75 for FourierFT with 72K params.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| use Uni-LoRA instead of Fastfood projection (ablation) | LoRA projection on RoBERTa-large · MRPC | score: 90.7 -> 91.3 | Helped |
| use Uni-LoRA instead of Fastfood projection (ablation) | LoRA projection on RoBERTa-large · MRPC | training time: 26 -> 9 mins | Helped |
| add global rather than layer-wise local projection (ablation) | Uni-LoRA on RoBERTa-large · GLUE, MRPC | score: 90.9\textsubscript{$\pm$0.8} -> 91.3\textsubscript{$\pm$0.6} | Helped |
| add global rather than layer-wise local projection (ablation) | Uni-LoRA on RoBERTa-large · GLUE, SST-2 | score: 96.2\textsubscript{$\pm$0.3} -> 96.3\textsubscript{$\pm$0.2} | Helped |
| add global rather than layer-wise local projection (ablation) | Uni-LoRA on RoBERTa-large · GLUE, QNLI | score: 94.5\textsubscript{$\pm$0.1} -> 94.6\textsubscript{$\pm$0.4} | Helped |
| add global rather than layer-wise local projection (ablation) | Uni-LoRA on RoBERTa-large · GLUE, CoLA | score: 68.5\textsubscript{$\pm$1.3} -> 68.5\textsubscript{$\pm$1.1} | No clear effect |
| add uniform rather than non-uniform projection (ablation) | Uni-LoRA on RoBERTa-large · GLUE, MRPC | score: 90.7\textsubscript{$\pm$0.6} -> 91.3\textsubscript{$\pm$0.6} | Helped |
| add uniform rather than non-uniform projection (ablation) | Uni-LoRA on RoBERTa-large · GLUE, CoLA | score: 67.0\textsubscript{$\pm$1.5} -> 68.5\textsubscript{$\pm$1.1} | Helped |
| add uniform rather than non-uniform projection (ablation) | Uni-LoRA on RoBERTa-large · GLUE, SST-2 | score: 96.1\textsubscript{$\pm$0.4} -> 96.3\textsubscript{$\pm$0.2} | Helped |
| add uniform rather than non-uniform projection (ablation) | Uni-LoRA on RoBERTa-large · GLUE, QNLI | score: 94.0\textsubscript{$\pm$0.4} -> 94.6\textsubscript{$\pm$0.4} | Helped |
| increase the trainable subspace dimension (ablation) | Uni-LoRA · SST-2, GSM8K, and MATH | accuracy | Mixed |
| vary LoRA rank (ablation) | Uni-LoRA · SST-2, GSM8K, and MATH | accuracy | No clear effect |
Surprising findings
- A single random, frozen, isometric projection of the full LoRA parameter space matches learned-projection VB-LoRA on GLUE despite having far fewer trainable parameters.
- Uni-LoRA with uniform global projection outperforms a non-uniform (A/B split) projection and a layer-wise local projection on the controlled ablations.
Limitations
- Only evaluated on small to medium scale NLP and CV benchmarks due to limited compute, as the authors state.
- On MATH with Gemma-7B, Uni-LoRA (28.94) is below LoRA (31.28) and for some comparisons it trails baselines such as VeRA on Mistral MATH.
Experimental setup
Datasets: GLUE SST-2 MRPC CoLA QNLI RTE STS-B MetaMathQA GSM8K MATH Cleaned Alpaca MT-Bench
Benchmarks: GLUE GSM8K MATH MT-Bench OxfordPets StanfordCars CIFAR10 DTD EuroSAT FGVC RESISC45 CIFAR100
Metrics: accuracy Matthews correlation Pearson correlation MT-Bench score training time GPU memory
Baselines: LoRA Tied-LoRA VeRA VB-LoRA LoRA-XS FourierFT Fastfood projection Full-FT
Builds on: LoRA Tied-LoRA VeRA VB-LoRA FourierFT Fastfood
Closest papers by meaning
- Beyond Higher Rank: Token-wise Input-Output Projections for Efficient Low-Rank Adaptation (NeurIPS 2025 · similarity 0.94)
- AuroRA: Breaking Low-Rank Bottleneck of LoRA with Nonlinear Mapping (NeurIPS 2025 · similarity 0.94)
- VB-LoRA: Extreme Parameter Efficient Fine-Tuning with Vector Banks (NeurIPS 2024 · similarity 0.94)
- LoRA-One: One-Step Full Gradient Could Suffice for Fine-Tuning Large Language Models, Provably and Efficiently (ICML 2025 · similarity 0.93)
- Learning Rate Matters: Vanilla LoRA May Suffice for LLM Fine-tuning (NeurIPS 2026 · similarity 0.93)
- GoRA: Gradient-driven Adaptive Low Rank Adaptation (NeurIPS 2025 · similarity 0.93)
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